Interesting, if slightly goady, thread.
I'm in one of those equal relationships. I have a very low tolerance for doing more than my fair share of housework. DC have been brought up to do their own laundry, make their own packed lunches etc since they started secondary school. Everyone cleans the toilet after they've used it. Other cleaning/cooking is done by rota.
I'm the same person who, in a different relationship, found myself doing way more than my fair share having had DC despite never noticing it before. When I tackled him on it, he became psychologically abusive. I left shortly afterwards when the increasing rows turned physical.
I've done a lot of thinking about this and laud the post above which explains that not pulling your weight domestically can be a form of domestic abuse.
I think it's really important to understand that none of this happens in a vacuum.
Humans are a social species and we're status driven. Our home and belongings are not just seen as our safe places but also as representative of ourselves . Across many cultures it's desirable to have a warm, welcoming home and to be hospitable. Men want this too! We all want to live somewhere safe and pleasant and to feel pride when someone comes to see us in it. It's natural, therefore, to make an effort to keep our homes pleasant. No one should feel dismissed for taking pride in making a nice home. Barring OCD-levels of cleaning, this is a natural behaviour IMO. The problem is not what some (mainly women) are doing. It's what some (mainly men) are not doing.
We also have a persistent gender pay gap that, funnily enough, is largely explained by the fact that women have children, since it largely doesn't exists until that point. The biggest way to reduce the gender pay gap would be that women stop having DC, but no one suggests that.
We also happen to live in a society where home making and child care doesn't count towards GDP. It has no 'real' economic value (unless you have to buy it, of course).
Our social set up actually encourage this division of labour since someone has to have the children and raise them but the state doesn't want to subsidise that, placing the responsibility on individual families. Since few families will earn enough to comfortably pay for a full time nanny, one parent nearly always ends up scaling back or giving up work completely and it's usually the mother because of things like breastfeeding and social expectations.
So, even for many women who have maintained independence until having children, it's not uncommon to find themselves on a lesser salary (or devoid of one completely) having children. In a society that says there is only a moral value to being a good mum, not a financial one. Many respond by trying to "pull their weight" in other ways, even if their DH doesn't actually expect that of them. And our patriarchal society encourages this.